Folded and spiral-tube screw-in compact fluorescent (CFL) bulbs are in wide use today, par-ticularly as they are popular as energy-saving, nominally “green” alternatives to incandescent bulbs, since they provide equivalent light lumens at lower wattage and their service life is longer. For example, typical 13 watt fluorescent bulbs are equivalent replacements for 60 watt incandescent bulbs, and 26 watt fluorescents replace 100 watt incandescent bulbs. In addition, the fluorescent bulbs operate much cooler, and can be handled even after being ON for several hours without burning the skin. Indeed, more folded and spiral-tube type screw-in fluorescent bulbs are sold than incandescent bulbs.
The spiral tube CFL bulb was invented in 1976 by Edward E. Hammer, an engineer with General Electric, in response to the 1973 oil crisis, but the invention was shelved. The design was eventually copied by others.1 It was not until 1995 that spiral CFL bulbs manufactured in China were commercially available. In 1980, Philips introduced its model SL, which was a screw-in bulb having an integral ballast. The SL bulb used a folded T4 tube, stable tri-color phosphors, and a mercury amalgam. This was the first successful screw-in replacement for an incandescent lamp. However, it was not until 1985 that the market really took off as a result of the introduction by the Osram company of the first CFL having an electronic ballast. The electronic ballast reduced the flickering and hum of the standard fluorescent tube ballasts. Today CFL bulbs fit in the same volume as standard incandescent bulbs as a result of new, high efficiency phosphors that permit more power per unit area per lumen, thereby permitting reduction in bulb size. CFLs typically radiate light in a different spectral range than that of incandescent bulbs. Improved phosphor formulations have resulted in the perceived color of soft-white CFL bulb light to be on par with standard incandescent lamps.
The average rated life of a CFL is between 8 and 15 times that of incandescent bulbs. CFLs typically have a rated lifespan of between 6,000 and 15,000 hours, whereas incandescent lamps are usually manufactured to have a lifespan of 750 hours or 1,000 hours. Although CFLs produce less light later in their lives than when they are new, the light output decay is exponential, with the fastest losses being soon after the lamp is first used. By the end of their lives, CFLs can be expected to produce 70-80% of their original light output, but since the response of the human eye to light is logarithmic, the CFL late-in-life 20-30% light output decline will be compensated for by the eyes.
For a given light output, CFLs use 20 to 33 percent less power than equivalent light-output incandescent bulbs. Since lighting accounted for approximately 9% of household electricity usage in the United States in 2001, widespread use of CFLs can save as much as 7% of total US household power, hence the phase-out of incandescent bulbs has been mandated by the government.
However, like all fluorescents, CFL bulb tubes contain a coating of a mercury amalgam and complex phosphors. While this coating accounts for the improved energy efficiency of CFLs, it seriously complicates their disposal, especially in cases where tubes are broken, as both are hazardous materials. Current CFLs sold are in large percentage, bare bulbs, with no means of proper pick-up, handling and disposal of broken, phosphor/mercury amalgam-coated glass shards. At best the manufacturers, distributors, sellers and government safety agencies simply rely on a warning to the consumer that they contain mercury and the consumer should take care to “properly dispose of used or broken bulbs”. Many refuse pick-up services decline to handle broken or used fluorescent bulbs, whether the standard 2′-4′ tubes, or the folded/spiral CFLs.
In addition, most people find the shape and folds of the folded-tube fluorescent bulbs to be unacceptable, if not downright ugly, from aesthetic and design viewpoints. Accordingly, some fluorescents are being offered that are encased or encapsulated in translucent white plastic or glass covers that mimic traditional incandescent light bulb shapes. These covers are formed secured to the metal thread base, and are spaced from the folded fluorescent tubes of the bulbs. As a result, the bases are enlarged, and do not fit in many lamp sockets. Accordingly, there remain a vast number of bare spiral and folded-tube bulbs in use that are not the preference of users and present a disposal and breakage hazard. In addition, those covers cause light loss, requiring the consumer to use higher-wattage CFLs, thereby defeating the cost savings. Indeed, in some cases users retain incandescent bulbs rather than use the spiral or folded-tube fluorescents because of light loss, design or aesthetic considerations.
Finally, fluorescent bulb light output is perceived as harsh, cold and giving a greenish tinge to objects illuminated. It can be particularly objectionable as not providing warmth to skin tones.
Accordingly, there is a need in the art for a way that permits covering of folded or spiral-tube CFL bulbs to make them safe to handle during installation, removal and clean-up when broken, are design and aesthetically acceptable, permit use of small bases in screw-in socket assemblies that have small clearance constraints, yet are inexpensive, easy to manufacture, and permit a wide range of design variations, including decorative and functional shades.